Crimping process



United States Patent Qt of New York No Drawing. Filed May 4, 1960, Ser.No. 26,702 2 Claims. (Cl. 28-72) This invention relates to a process forcrimping, specifically, drawn nylon 6 yarn carrying a lubricant finishthereon, said process being of the type wherein the yarn is forced intoa pressure crimping zone. My process is especially suitable for use withheavy denier multi-filament yarns having denier of say 10005000 andfilament count of say about 50-250.

Crimpers of the general type employed in my process are well-known,being disclosed for example in U.S.P. 2,734,228 of February 14, 1956 toW. D. Hay for Crimping Apparatus; USP. 2,763,898 of September 25, 1956to C. W. Sammons et al. for Treatment of Textile Fibers; U.S.P.2,865,080 of December 23, 1958 to R. A. A. Hentschel for Method andApparatus for Crimping and Relaxing Filaments and U.S.P. 2,888,733 ofJune 2, 1959 to Harry Wegener for Process for the Fixation of PressureCrimped Synthetic Fibers. When used upon heavy denier yarns, however,especially simultaneously upon several ends of such yarns, the prior artcrimpers tend to be unsatisfactory with respect to uniformity of crimpfrequency obtained therewith.

I have found that important factors in obtaining uni-' form crimpfrequency in a stutter box crimper of the type above discussed are themoisture content of the yarn entering the crimping chamber, and thetemperature of the entering yarn. My process described below providesexcellent control over these moisture and yarn temperature factors.

My process comprises contacting a drawn nylon 6 yarn carrying alubricant finish thereon with dry steam in a steaming zone prior tointroduction of the yarn into the crimping chamber, said dry steam beingat or slightly above saturation temperature and pressure. To establishthe desired temperature and moisture content of the steam used fortreating the yarn, I have found it is important to maintain the steaminitially at a temperature of at least about 103 C. and not above about130 C. and at a superatmospheric pressure constant within about 2 ouncesper square inch, just before the steaming zone. Thereby temperaturevariations both in this steam under pressure and in the steam within thesteaming zone can be maintained within about 1 C.

Further in accordance with my invention, the yarn thus treated withsteam is fed at moisture content of about 2-3% by weight into thecrimping chamber and receives no supply of heat and no setting agentother than said steam. Moreover, in accordance with my invention theyarn in the crimping zone is at a temperature between about 60 C. andabout 90 C. The desired temperature and moisture content of the yarnwill usually be obtained using steam as above specified within a shortcontact time of the order of about 1 second. The yarn temperatureresulting from this contact may be close to that of the steam itself,but in general the yarn will cool in the crimping chamber as the resultof heat losses therefrom, thus reaching the desired temperature range ofabout 60- 90 C.

While I do not intend to be bound by any mere theories of the operationof my process, I believe that use of dry rather than Wet steam isimportant because drops of moisture on the yarn will result in randomremoval of lubricating finish therefrom thus causing random variation inthe friction between the yarn and the crimping chamber, with consequentvariation in the pressure with- 3,031,734 Patented May 1, 1962 MIC inthe crimping chamber. Such pressure variations result in variations incrimping frequency. Moreover, drops of water on the yarn will tend toproduce random localized cooling and this cooling will affect the natureof the crimp at the cooled spot. Apparently the crimping frequency issensitive to yarn pressure and also to moisture content and temperatureof the yarn. Maintenance of a yarn temperature in the main body of thecrimping chamber between about 60 C. and about C. apparently isdesirable to limit crimping action to the zone immediately adjacent theinlet nip of the feed rolls. A moisture content of the entering yarn ofabout 23% by weight, with the entering yarn at temperature near that ofthe steam employed, say about C. C., appears to represent a favorablecombination of conditions for obtaining a uniform crimp frequency ofabout 10-15 crimps per inch in a heavy denier drawn nylon 6 yarn.

Preferred operating conditions in my process involve maintaining thetemperature of the steam while under pressure, just before the steamenters the steaming zone, in the range between about C. and about C. andthe pressure of this steam in the range between about 3 and about 5p.s.i.g., and maintaining the steam in the steaming zone at aboutatmospheric pressure and atabout 101 C. These conditions can beestablished by generating steam at say 15 p.s.-i.g. and then reducingthe pressure on this steam through an automatically controlled valvewhile maintaining back pressure by use of an orifice with a very smallopening just ahead of the inlet to the steaming zone. To compensate forheat losses in the piping carrying the steam under pressure, asuperheater is desirably provided having means for automatically controlling the steam temperature within about 1 C. For best control thesteam temperature and steam pressure should be sensed as near aspossible to the orifice which creates the back pressure.

The steam leaving the orifice suitably enters a tube serving as steamingzone, at the bottom thereof and about at a mid-point. Desirably thesteam tube is tilted away from the crimper so as to drain any condensatewithout allowing the condensate to contact the yarn. Desirably also ablower is provided at the exit from the steam tube to withdraw the steambefore it can contact the crimper feed rolls and condense thereon. Underthe preferred conditions above outlined I find the crimps formed in theyarn include both sharp V-bends and round bends.

A particularly suitable crimper of the stuffing box type for use in myprocess is described in detail in my copending application Serial No.26,876 filed simultaneously herewith, wherein a sensitive switch isactuated by motion of the gate of the crimper to stop the feed rollswhen the yarn volume in the crimping chamber reaches a predeterminedpoint, and the opposite motion of the gate is limited by a stop bar orthe like.

The examples, data for which is set out in the table below, representspecific embodiments of the best mode contemplated by me for carryingout my invention but are intended to be illustrative only, and theinvention is not to be considered as limited to all details: of theexamples.

In the below examples the nylon 6 yarn employed was of 2100 denier and112 filament count and had from 0 t0 1/2Z twist per inch. It wasproduced generally in conventional manner by melt spinning, applying alubricating oil emulsion finish to the spun filament, drawing thefilament on a draw twister over a snubbing pin and a heated block andtaking up on a pirn. Six ends of this yarn were threaded through eyeholes in the inlet and outlet of a steam tube about 29" long. The steamwas initially maintained at back pressures constant within 2 ounces persquare inch ranging between 3 and p.s.i.g, and at temperatures,corresponding to said pressures, constant within 1 C. and ranging from104 C. to 109 C. The steam was withdrawn from the tube by pipes and ablower, to avoid condensation on the crimper feed rolls.

This steam had saturation temperature of about 101 C. corresponding tosaturation pressure of about 1 /2 p.s.i.g. The steam outlets from thesteam tube were small enough to maintain the steam under slightsuperatmospheric pressure therein. The steam when allowed to issue intothe air from the steam tube did not condense to a fog until it hadcooled slightly in the air. The temperature of the steam tube was 101011 C.

The six yarn ends were withdrawn to the crimper as a fiat ribbon fromthe steam tube. The rate of yarn feed to the crimper in feet per minutevaried from 730 to 770; the weight on the crimper gate was 1 pound; themaximum movement of the gate was 3 and the rate of winding up thecrimped yarn varied from 560-570 feet per minute, being adjusted to takeup the yarn slightly slow er (on a weight basis) than the yarn was fedwhereby the switch periodically stopped the feed rolls momentarily. Thetemperature of the yarn entering the crimper was about that of the steamtube, say about 95 100 C. and may have risen just beyond the nip rolls;but in the main body of the crimping chamber the yarn was about 70 C.and its moisture content entering the crimper was about 2.5% by weight.

Average 30 tests, crimps per inch. b Average 18 tests (crimpedlength/straight length) X 100.

The control of crimp frequencies obtained in the above examples wasexcellent, the range being between 10 and 11 crimps per inch in alltests. Yarn with these controlled crimp frequencies shows gooduniformity in dyeing, important in most commercial applications.

I claim:

1. A process of crimping drawn nylon 6 yarn carrying a lubricant finishthereon by forcing the yarn into a pressure crimping zone, which processcomprises contacting said yarn with dry steam in a steaming zone priorto introduction of the yarn into the crimping zone, said dry steam beingat about its saturation temperature and pressure and being maintainedjust before said steaming zone at higher temperature of at least about103 C. and not above about 130 C. and at a superatmospheric pressureconstant within about 2 ounces per square inch, the temperaturevariations in this steam under pressure and in the steam in the steamingzone being maintained within about 1 C.; and feeding said yarn withmoisture content of about 23% by weight into a crimping zone; said drysteam being the sole source of heat and the sole setting agent appliedto the yarn and said yarn being at a temperature in the main body of thecrimping zone between about C. and about C. and at higher temperature atthe entrance thereto than in the main body.

2. Process as defined in claim 1 wherein the temperature of the steamunder pressure just before inlet to the References Cited in the file ofthis patent UNITED STATES PATENTS 2,734,228 Hay Feb. 14, 1956 Hitt May29, 1956.

